Pressure sensors based on the MEMS (Micro Electro Mechanical Systems) technique include a piezoelectric sensor, piezoresistive sensor, capacitance sensor, and the like. On the other hand, a pressure sensor using the spin technique whose sensing principle is different from that of the above-described pressure sensors has been proposed. In the pressure sensor using the spin technique, a spin valve magnetostrictive element (also called a magnetoresistive (MR) element) detects a resistance change corresponding to an anisotropic strain caused by an external pressure. Demands have arisen for increasing the sensitivity of the pressure sensor using the spin technique.